Stacking of network switching devices can bring together and closely integrate computation, storage and networking, enabling a more seamless approach to management and configuration. A stack system comprises a plurality of network switching devices which are connected together. The network switching devices in the stack system may be referred to as “member devices” of the stack system. In some cases the member devices may be configured to act as a single virtual device when receiving and forwarding packets to devices outside the stack system.
A two-level vertical stack network architecture is used in some data centers. The vertical stack network may include first and second levels as follows.
A first level comprises a stack system of connected member devices, which may be referred to as Core Backbone (CB) devices. In some examples the CB devices are connected in a ring topology. The links connecting the CB devices to each other are referred to as “stack links”.
A second level comprises Port Extender (PE) devices which are connected to the CB devices in the first level. In the two-level vertical stack network, these PE devices are not connected to each other on the second level through stack links, but are indirectly connected to each other via the CB devices.